Dual Nature of Radiation and Matter

Photo Electric Effect


The phenomenon of photoelectric effect is discovered by Hertz in 1887

When the light of certain frequency is allowed to fall on a metal surface and electrons are ejected from the metal surface this phenomenon is called photoelectric effect
Or
The phenomenon of emission of electrons by metals when illuminated by light of suitable frequency

The photoelectric effect involves the conversion of light energy into electrical energy

Photo Electrons --
The ejected electrons from the metal surface when is suitable frequency of light falls on that metal surface are called photoelectrons
Number of photo electrons ejected =
Power / energy of photon

Threshold Frequency --
The minimum amount of frequency of incident light required to eject an electron from the metal surface is known as threshold frequency

Work function --

The minimum energy required by an electron to escape from the metal surface is called work function it is also known as threshold energy

Work function = h v o
Work function is measured in electron volt
1 eV = 1.602×10^-¹⁹. J

The work function depends --
1) properties of metal
2) nature of surface

Photons --
Light consists of packets of energy called photons photons are electrically neutral and not deflected by electric and magnetic field
Energy of photon -- hv.= hc/£
where
£ is wavelength ie lambda h is planck constant and v is frequency
Number of photons emitted = power / energy of photon


The photoelectric current
The photoelectric current depends upon
1) intensity of the light
2) Potential difference applied between electrodes
3) nature of the emitter material


Cutoff voltage -- cutoff voltage is also known as stopping potential it depends upon
Cut off voltage is directly related to maximum kinetic energy of the emitted electrons

eVo = ½mv²

Stopping potential depends on

Frequency of incident light


Sun Dec 25, 2022

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